import abc


class bproto_Package(abc.ABC):
    @abc.abstractmethod
    def to_bytes(self) -> bytes:
        raise NotImplementedError()
    
    @abc.abstractmethod
    def from_bytes(self, data: bytes):
        raise NotImplementedError()
    

class bproto_Bitfield(abc.ABC):
    @abc.abstractmethod
    def to_bytes(self) -> bytes:
        pass
    
    @abc.abstractmethod
    def from_bytes(self, data: bytes):
        pass
    
    def __str__(self):
        return self.__repr__()


def crc16_calc_inital(data: bytearray) -> int:
    """CRC-16/CITT-FALSE
    from https://stackoverflow.com/questions/35205702/calculating-crc16-in-python

    Args:
        data (bytearray): protocol hash

    Returns:
        bytes: initals for crc16_calc_with_initial
    """
    crc = 0xFFFF
    for i in range(0, len(data)):
        crc ^= data[i] << 8
        for j in range(0, 8):
            if (crc & 0x8000) > 0:
                crc = (crc << 1) ^ 0x1021
            else:
                crc = crc << 1
    return crc


def calc_crc_sum(data: bytearray, inital: int) -> bytes:
    """CRC-16/CITT-FALSE
    form https://stackoverflow.com/questions/35205702/calculating-crc16-in-python
    
    Args:
        data (bytearray): protocol data
        inital (int): Inital calculated from protocol hash

    Returns:
        bytes: 2 byte CRC Checksum
    """
    crc = inital
    for i in range(0, len(data)):
        crc ^= data[i] << 8
        for j in range(0, 8):
            if (crc & 0x8000) > 0:
                crc = (crc << 1) ^ 0x1021
            else:
                crc = crc << 1
    return crc & 0xFFFF